Commit Graph

552 Commits

Author SHA1 Message Date
Sebastian Pop
ad43499fc4 dependence analysis
Patch from Preston Briggs <preston.briggs@gmail.com>.

This is an updated version of the dependence-analysis patch, including an MIV
test based on Banerjee's inequalities.

It's a fairly complete implementation of the paper

    Practical Dependence Testing
    Gina Goff, Ken Kennedy, and Chau-Wen Tseng
    PLDI 1991

It cannot yet propagate constraints between coupled RDIV subscripts (discussed
in Section 5.3.2 of the paper).

It's organized as a FunctionPass with a single entry point that supports testing
for dependence between two instructions in a function. If there's no dependence,
it returns null. If there's a dependence, it returns a pointer to a Dependence
which can be queried about details (what kind of dependence, is it loop
independent, direction and distance vector entries, etc). I haven't included
every imaginable feature, but there's a good selection that should be adequate
for supporting many loop transformations. Of course, it can be extended as
necessary.

Included in the patch file are many test cases, commented with C code showing
the loops and array references.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165708 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-11 07:32:34 +00:00
James Molloy
9e36496eb3 Add default JIT LIT variable.
Patch by David Tweed!



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164996 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-02 10:57:08 +00:00
Duncan Sands
44401b7c80 Now that invoke of an intrinsic is possible (for the llvm.do.nothing intrinsic)
teach the callgraph logic to not create callgraph edges to intrinsics for invoke
instructions; it already skips this for call instructions.  Fixes PR13903.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164707 91177308-0d34-0410-b5e6-96231b3b80d8
2012-09-26 17:16:01 +00:00
Arnold Schwaighofer
3d5f96ee1b BasicAA: Recognize cyclic NoAlias phis
Enhances basic alias analysis to recognize phis whose first incoming values are
NoAlias and whose other incoming values are just the phi node itself through
some amount of recursion.

Example: With this change basicaa reports that ptr_phi and ptr_phi2 do not alias
each other.

bb:
 ptr = ptr2 + 1

loop:
  ptr_phi = phi [bb, ptr], [loop, ptr_plus_one]
  ptr2_phi = phi [bb, ptr2], [loop, ptr2_plus_one]
  ...
  ptr_plus_one = gep ptr_phi, 1
  ptr2_plus_one = gep ptr2_phi, 1

This enables the elimination of one load in code like the following:

extern int foo;

int test_noalias(int *ptr, int num, int* coeff) {
  int *ptr2 = ptr;
  int result = (*ptr++) * (*coeff--);
  while (num--) {
    *ptr2++ = *ptr;
    result +=  (*coeff--) * (*ptr++);
  }
  *ptr = foo;
  return result;
}

Part 2/2 of fix for PR13564.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163319 91177308-0d34-0410-b5e6-96231b3b80d8
2012-09-06 14:41:53 +00:00
Arnold Schwaighofer
029032693f BasicAA: GEPs of NoAlias'ing base ptr with equivalent indices are NoAlias
If we can show that the base pointers of two GEPs don't alias each other using
precise analysis and the indices and base offset are equal then the two GEPs
also don't alias each other.
This is primarily needed for the follow up patch that analyses NoAlias'ing PHI
nodes.

Part 1/2 of fix for PR13564.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163317 91177308-0d34-0410-b5e6-96231b3b80d8
2012-09-06 14:31:51 +00:00
NAKAMURA Takumi
c3c237d8be llvm/test/Analysis/Profiling: Mark 3 of them as REQUIRES: loadable_module.
FIXME: profile_rt.dll could be built on win32.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162811 91177308-0d34-0410-b5e6-96231b3b80d8
2012-08-29 00:37:46 +00:00
Manman Ren
d26200423e Profile: set branch weight metadata with data generated from profiling.
This patch implements ProfileDataLoader which loads profile data generated by
-insert-edge-profiling and updates branch weight metadata accordingly.

Patch by Alastair Murray.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162799 91177308-0d34-0410-b5e6-96231b3b80d8
2012-08-28 22:21:25 +00:00
Manman Ren
1a710fdde1 BranchProb: modify the definition of an edge in BranchProbabilityInfo to handle
the case of multiple edges from one block to another.

A simple example is a switch statement with multiple values to the same
destination. The definition of an edge is modified from a pair of blocks to
a pair of PredBlock and an index into the successors.

Also set the weight correctly when building SelectionDAG from LLVM IR,
especially when converting a Switch.
IntegersSubsetMapping is updated to calculate the weight for each cluster.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162572 91177308-0d34-0410-b5e6-96231b3b80d8
2012-08-24 18:14:27 +00:00
Benjamin Kramer
4e81d40545 Fix broken check lines.
I really need to find a way to automate this, but I can't come up with a regex
that has no false positives while handling tricky cases like custom check
prefixes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162097 91177308-0d34-0410-b5e6-96231b3b80d8
2012-08-17 12:28:26 +00:00
Nadav Rotem
8dff60e96a MemoryDependenceAnalysis attempts to find the first memory dependency for function calls.
Currently, if GetLocation reports that it did not find a valid pointer (this is the case for volatile load/stores),
we ignore the result. This patch adds code to handle the cases where we did not obtain a valid pointer.

rdar://11872864  PR12899



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161802 91177308-0d34-0410-b5e6-96231b3b80d8
2012-08-13 23:03:43 +00:00
Nick Lewycky
6ce2471806 Stay rational; don't assert trying to take the square root of a negative value.
If it's negative, the loop is already proven to be infinite. Fixes PR13489!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161107 91177308-0d34-0410-b5e6-96231b3b80d8
2012-08-01 09:14:36 +00:00
Chandler Carruth
1de43ede89 Fix the remaining TCL-style quotes found in the testsuite. This is
another mechanical change accomplished though the power of terrible Perl
scripts.

I have manually switched some "s to 's to make escaping simpler.

While I started this to fix tests that aren't run in all configurations,
the massive number of tests is due to a really frustrating fragility of
our testing infrastructure: things like 'grep -v', 'not grep', and
'expected failures' can mask broken tests all too easily.

Essentially, I'm deeply disturbed that I can change the testsuite so
radically without causing any change in results for most platforms. =/

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159547 91177308-0d34-0410-b5e6-96231b3b80d8
2012-07-02 19:09:46 +00:00
Chandler Carruth
49589f0d0e Convert the uses of '|&' to use '2>&1 |' instead, which works on old
versions of Bash. In addition, I can back out the change to the lit
built-in shell test runner to support this.

This should fix the majority of fallout on Darwin, but I suspect there
will be a few straggling issues.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159544 91177308-0d34-0410-b5e6-96231b3b80d8
2012-07-02 18:37:59 +00:00
Chandler Carruth
4177e6fff5 Convert all tests using TCL-style quoting to use shell-style quoting.
This was done through the aid of a terrible Perl creation. I will not
paste any of the horrors here. Suffice to say, it require multiple
staged rounds of replacements, state carried between, and a few
nested-construct-parsing hacks that I'm not proud of. It happens, by
luck, to be able to deal with all the TCL-quoting patterns in evidence
in the LLVM test suite.

If anyone is maintaining large out-of-tree test trees, feel free to poke
me and I'll send you the steps I used to convert things, as well as
answer any painful questions etc. IRC works best for this type of thing
I find.

Once converted, switch the LLVM lit config to use ShTests the same as
Clang. In addition to being able to delete large amounts of Python code
from 'lit', this will also simplify the entire test suite and some of
lit's architecture.

Finally, the test suite runs 33% faster on Linux now. ;]
For my 16-hardware-thread (2x 4-core xeon e5520): 36s -> 24s

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159525 91177308-0d34-0410-b5e6-96231b3b80d8
2012-07-02 12:47:22 +00:00
Nick Lewycky
4d3bba5be4 If the step value is a constant zero, the loop isn't going to terminate. Fixes
the assert reported in PR13228!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159393 91177308-0d34-0410-b5e6-96231b3b80d8
2012-06-28 23:44:57 +00:00
Andrew Trick
fe3516f9a5 SCEV: Handle a corner case reducing AddRecExpr * AddRecExpr
If integer overflow causes one of the terms to reach zero, that can
force the entire expression to zero.

Fixes PR12929: cast<Ty>() argument of incompatible type

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157673 91177308-0d34-0410-b5e6-96231b3b80d8
2012-05-30 03:35:20 +00:00
Andrew Trick
8aa22019ca SCEV: Add MarkPendingLoopPredicates to avoid recursive isImpliedCond.
getUDivExpr attempts to simplify by checking for overflow.
isLoopEntryGuardedByCond then evaluates the loop predicate which
may lead to the same getUDivExpr causing endless recursion.

Fixes PR12868: clang 3.2 segmentation fault.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157092 91177308-0d34-0410-b5e6-96231b3b80d8
2012-05-19 00:48:25 +00:00
Bill Wendling
75920ad424 FileCheck-ize tests.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155434 91177308-0d34-0410-b5e6-96231b3b80d8
2012-04-24 10:45:44 +00:00
Bill Wendling
c6490d138f FileCheck-ize these tests.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155433 91177308-0d34-0410-b5e6-96231b3b80d8
2012-04-24 10:36:42 +00:00
Bill Wendling
d5cc8b81ca FileCheck-ize these tests. Harden some of them.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155432 91177308-0d34-0410-b5e6-96231b3b80d8
2012-04-24 09:15:38 +00:00
Benjamin Kramer
86df062791 Revert "SCEV: When expanding a GEP the final addition to the base pointer has NUW but not NSW."
This isn't right either, reverting for now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154910 91177308-0d34-0410-b5e6-96231b3b80d8
2012-04-17 06:33:57 +00:00
Benjamin Kramer
c77764591b SCEV: When expanding a GEP the final addition to the base pointer has NUW but not NSW.
Found by inspection.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154262 91177308-0d34-0410-b5e6-96231b3b80d8
2012-04-07 17:19:26 +00:00
Rafael Espindola
8f3fabe0fe Handle intrinsics in GlobalsModRef. Fixes pr12351.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153604 91177308-0d34-0410-b5e6-96231b3b80d8
2012-03-28 21:31:24 +00:00
Andrew Trick
eb6dd23c95 SCEV fix: Handle loop invariant loads.
Fixes PR11882: NULL dereference in ComputeLoadConstantCompareExitLimit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153480 91177308-0d34-0410-b5e6-96231b3b80d8
2012-03-26 22:33:59 +00:00
Andrew Trick
54e3adea34 Test scalar evolution directly instead of testing the result of
canonical indvars.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153256 91177308-0d34-0410-b5e6-96231b3b80d8
2012-03-22 17:09:31 +00:00
Eli Friedman
cd38485b8a Duncan pointed out that if the alignment isn't explicitly specified, it defaults to the ABI alignment. Given that, make this code a bit more aggressive in such cases.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151584 91177308-0d34-0410-b5e6-96231b3b80d8
2012-02-27 23:16:46 +00:00
Eli Friedman
1680a24e53 Teach BasicAA about the LLVM IR rules that allow reading past the end of an object given sufficient alignment. Fixes PR12098.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151553 91177308-0d34-0410-b5e6-96231b3b80d8
2012-02-27 20:46:07 +00:00
Rafael Espindola
c9ae8cc24c Change the implementation of dominates(inst, inst) to one based on what the
verifier does. This correctly handles invoke.
Thanks to Duncan, Andrew and Chris for the comments.
Thanks to Joerg for the early testing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151469 91177308-0d34-0410-b5e6-96231b3b80d8
2012-02-26 02:19:19 +00:00
Eli Bendersky
0f0c411079 Replace all instances of dg.exp file with lit.local.cfg, since all tests are run with LIT now and now Dejagnu. dg.exp is no longer needed.
Patch reviewed by Daniel Dunbar. It will be followed by additional cleanup patches.




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150664 91177308-0d34-0410-b5e6-96231b3b80d8
2012-02-16 06:28:33 +00:00
Nick Lewycky
b48a18903a Change CaptureTracking to pass a Use* instead of a Value* when a value is
captured. This allows the tracker to look at the specific use, which may be
especially interesting for function calls.

Use this to fix 'nocapture' deduction in FunctionAttrs. The existing one does
not iterate until a fixpoint and does not guarantee that it produces the same
result regardless of iteration order. The new implementation builds up a graph
of how arguments are passed from function to function, and uses a bottom-up walk
on the argument-SCCs to assign nocapture. This gets us nocapture more often, and
does so rather efficiently and independent of iteration order.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147327 91177308-0d34-0410-b5e6-96231b3b80d8
2011-12-28 23:24:21 +00:00
Chandler Carruth
51f40a725b Make the unreachable probability much much heavier. The previous
probability wouldn't be considered "hot" in some weird loop structures
or other compounding probability patterns. This makes it much harder to
confuse, but isn't really a principled fix. I'd actually like it if we
could model a zero probability, as it would make this much easier to
reason about. Suggestions for how to do this better are welcome.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147142 91177308-0d34-0410-b5e6-96231b3b80d8
2011-12-22 09:26:37 +00:00
Chandler Carruth
ddbc274169 Manually upgrade the test suite to specify the flag to cttz and ctlz.
I followed three heuristics for deciding whether to set 'true' or
'false':

- Everything target independent got 'true' as that is the expected
  common output of the GCC builtins.
- If the target arch only has one way of implementing this operation,
  set the flag in the way that exercises the most of codegen. For most
  architectures this is also the likely path from a GCC builtin, with
  'true' being set. It will (eventually) require lowering away that
  difference, and then lowering to the architecture's operation.
- Otherwise, set the flag differently dependending on which target
  operation should be tested.

Let me know if anyone has any issue with this pattern or would like
specific tests of another form. This should allow the x86 codegen to
just iteratively improve as I teach the backend how to differentiate
between the two forms, and everything else should remain exactly the
same.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146370 91177308-0d34-0410-b5e6-96231b3b80d8
2011-12-12 11:59:10 +00:00
Andrew Trick
ecb35ece5c SCEV fix. In general, Add/Mul expressions should not inherit NSW/NUW.
This reverts r139450, fixes r139453, and adds much needed comments and a
unit test.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145367 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-29 02:16:38 +00:00
Andrew Trick
d2b5e2dd44 Filecheckize.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145363 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-29 02:05:23 +00:00
Chris Lattner
d2bf432b2b Upgrade syntax of tests using volatile instructions to use 'load volatile' instead of 'volatile load', which is archaic.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145171 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-27 06:54:59 +00:00
Nick Lewycky
89d093d5b6 Don't forget to check FlagNW when determining whether an AddRecExpr will wrap
or not. Patch by Brendon Cahoon!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144173 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-09 07:11:37 +00:00
Benjamin Kramer
588d84c4df 2>&1 doesn't work here, it just creates an empty file called "&1"
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143117 91177308-0d34-0410-b5e6-96231b3b80d8
2011-10-27 18:27:45 +00:00
Duncan Sands
f8a9eb1fa6 Restore commits 142790 and 142843 - they weren't breaking the build
bots.  Original commit messages:
- Reapply r142781 with fix. Original message:

  Enhance SCEV's brute force loop analysis to handle multiple PHI nodes in the
  loop header when computing the trip count.

  With this, we now constant evaluate:
    struct ListNode { const struct ListNode *next; int i; };
    static const struct ListNode node1 = {0, 1};
    static const struct ListNode node2 = {&node1, 2};
    static const struct ListNode node3 = {&node2, 3};
    int test() {
      int sum = 0;
      for (const struct ListNode *n = &node3; n != 0; n = n->next)
        sum += n->i;
      return sum;
    }

- Now that we look at all the header PHIs, we need to consider all the header PHIs
  when deciding that the loop has stopped evolving. Fixes miscompile in the gcc
  torture testsuite!



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142919 91177308-0d34-0410-b5e6-96231b3b80d8
2011-10-25 12:28:52 +00:00
Chandler Carruth
45baf6bb85 Fix the API usage in loop probability heuristics. It was incorrectly
classifying many edges as exiting which were in fact not. These mainly
formed edges into sub-loops. It was also not correctly classifying all
returning edges out of loops as leaving the loop. With this match most
of the loop heuristics are more rational.

Several serious regressions on loop-intesive benchmarks like perlbench's
loop tests when built with -enable-block-placement are fixed by these
updated heuristics. Unfortunately they in turn uncover some other
regressions. There are still several improvemenst that should be made to
loop heuristics including trip-count, and early back-edge management.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142917 91177308-0d34-0410-b5e6-96231b3b80d8
2011-10-25 09:47:41 +00:00
Duncan Sands
526c80bae4 Speculatively revert commits 142790 and 142843 to see if it fixes
the dragonegg and llvm-gcc self-host buildbots.  Original commit
messages:
- Reapply r142781 with fix. Original message:

  Enhance SCEV's brute force loop analysis to handle multiple PHI nodes in the
  loop header when computing the trip count.

  With this, we now constant evaluate:
    struct ListNode { const struct ListNode *next; int i; };
    static const struct ListNode node1 = {0, 1};
    static const struct ListNode node2 = {&node1, 2};
    static const struct ListNode node3 = {&node2, 3};
    int test() {
      int sum = 0;
      for (const struct ListNode *n = &node3; n != 0; n = n->next)
        sum += n->i;
      return sum;
    }

- Now that we look at all the header PHIs, we need to consider all the header PHIs
when deciding that the loop has stopped evolving. Fixes miscompile in the gcc
torture testsuite!



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142916 91177308-0d34-0410-b5e6-96231b3b80d8
2011-10-25 09:26:43 +00:00
Nick Lewycky
3846163aee Now that we look at all the header PHIs, we need to consider all the header PHIs
when deciding that the loop has stopped evolving. Fixes miscompile in the gcc
torture testsuite!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142843 91177308-0d34-0410-b5e6-96231b3b80d8
2011-10-24 21:02:38 +00:00
Chandler Carruth
de1c9bb450 Remove return heuristics from the static branch probabilities, and
introduce no-return or unreachable heuristics.

The return heuristics from the Ball and Larus paper don't work well in
practice as they pessimize early return paths. The only good hitrate
return heuristics are those for:
 - NULL return
 - Constant return
 - negative integer return

Only the last of these three can possibly require significant code for
the returning block, and even the last is fairly rare and usually also
a constant. As a consequence, even for the cold return paths, there is
little code on that return path, and so little code density to be gained
by sinking it. The places where sinking these blocks is valuable (inner
loops) will already be weighted appropriately as the edge is a loop-exit
branch.

All of this aside, early returns are nearly as common as all three of
these return categories, and should actually be predicted as taken!
Rather than muddy the waters of the static predictions, just remain
silent on returns and let the CFG itself dictate any layout or other
issues.

However, the return heuristic was flagging one very important case:
unreachable. Unfortunately it still gave a 1/4 chance of the
branch-to-unreachable occuring. It also didn't do a rigorous job of
finding those blocks which post-dominate an unreachable block.

This patch builds a more powerful analysis that should flag all branches
to blocks known to then reach unreachable. It also has better worst-case
runtime complexity by not looping through successors for each block. The
previous code would perform an N^2 walk in the event of a single entry
block branching to N successors with a switch where each successor falls
through to the next and they finally fall through to a return.

Test case added for noreturn heuristics. Also doxygen comments improved
along the way.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142793 91177308-0d34-0410-b5e6-96231b3b80d8
2011-10-24 12:01:08 +00:00
Nick Lewycky
7c3fc57472 Reapply r142781 with fix. Original message:
Enhance SCEV's brute force loop analysis to handle multiple PHI nodes in the
  loop header when computing the trip count.

  With this, we now constant evaluate:
    struct ListNode { const struct ListNode *next; int i; };
    static const struct ListNode node1 = {0, 1};
    static const struct ListNode node2 = {&node1, 2};
    static const struct ListNode node3 = {&node2, 3};
    int test() {
      int sum = 0;
      for (const struct ListNode *n = &node3; n != 0; n = n->next)
        sum += n->i;
      return sum;
    }


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142790 91177308-0d34-0410-b5e6-96231b3b80d8
2011-10-24 06:57:05 +00:00
Nick Lewycky
38af3d5a8d Speculatively revert r142781. Bots are showing
Assertion `i_nocapture < OperandTraits<PHINode>::operands(this) && "getOperand() out of range!"' failed.
coming out of indvars.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142786 91177308-0d34-0410-b5e6-96231b3b80d8
2011-10-24 04:00:25 +00:00
Nick Lewycky
795cb48f1a Enhance SCEV's brute force loop analysis to handle multiple PHI nodes in the
loop header when computing the trip count.

With this, we now constant evaluate:
  struct ListNode { const struct ListNode *next; int i; };
  static const struct ListNode node1 = {0, 1};
  static const struct ListNode node2 = {&node1, 2};
  static const struct ListNode node3 = {&node2, 3};
  int test() {
    int sum = 0;
    for (const struct ListNode *n = &node3; n != 0; n = n->next)
      sum += n->i;
    return sum;
  }


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142781 91177308-0d34-0410-b5e6-96231b3b80d8
2011-10-23 23:43:14 +00:00
Chandler Carruth
14edd314af Teach the BranchProbabilityInfo pass to print its results, and use that
to bring it under direct test instead of merely indirectly testing it in
the BlockFrequencyInfo pass.

The next step is to start adding tests for the various heuristics
employed, and to start fixing those heuristics once they're under test.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142778 91177308-0d34-0410-b5e6-96231b3b80d8
2011-10-23 21:21:50 +00:00
Nick Lewycky
614fef6d5a Make SCEV's brute force analysis stronger in two ways. Firstly, we should be
able to constant fold load instructions where the argument is a constant.
Second, we should be able to watch multiple PHI nodes through the loop; this
patch only supports PHIs in loop headers, more can be done here.

With this patch, we now constant evaluate:
  static const int arr[] = {1, 2, 3, 4, 5};
  int test() {
    int sum = 0;
    for (int i = 0; i < 5; ++i) sum += arr[i];
    return sum;
  }


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142731 91177308-0d34-0410-b5e6-96231b3b80d8
2011-10-22 19:58:20 +00:00
Chandler Carruth
941aa7b1e8 Generalize the reading of probability metadata to work for both branches
and switches, with arbitrary numbers of successors. Still optimized for
the common case of 2 successors for a conditional branch.

Add a test case for switch metadata showing up in the BlockFrequencyInfo pass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142493 91177308-0d34-0410-b5e6-96231b3b80d8
2011-10-19 10:32:19 +00:00
Chandler Carruth
99d01c54a0 Teach the BranchProbabilityInfo analysis pass to read any metadata
encoding of probabilities. In the absense of metadata, it continues to
fall back on static heuristics.

This allows __builtin_expect, after lowering through llvm.expect
a branch instruction's metadata, to actually enter the branch
probability model. This is one component of resolving PR2577.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142492 91177308-0d34-0410-b5e6-96231b3b80d8
2011-10-19 10:30:30 +00:00
Chandler Carruth
6aa5c26c81 Add pass printing support to BlockFrequencyInfo pass. The implementation
layer already had support for printing the results of this analysis, but
the wiring was missing.

Now that printing the analysis works, actually bring some of this
analysis, and the BranchProbabilityInfo analysis that it wraps, under
test! I'm planning on fixing some bugs and doing other work here, so
having a nice place to add regression tests and a way to observe the
results is really useful.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142491 91177308-0d34-0410-b5e6-96231b3b80d8
2011-10-19 10:12:41 +00:00